In a substrate processing apparatus for performing plasma treatment, e.g., dry etching or film formation, on a semiconductor device wafer (hereinafter, simply referred to as “wafer”) as a substrate, a single lot including a plurality of, e.g., 25, wafers is supplied while being accommodated in a container (carrier). Further, in the substrate processing apparatus, wafers are taken one by one from the supplied carrier to be subjected to plasma treatment.
In order to manufacture a semiconductor device, it is required to perform several types of plasma treatments on a wafer. However, a single substrate processing apparatus cannot perform all the required plasma treatments on the wafer. Therefore, a few types of plasma treatments are performed on a wafer by a single substrate processing apparatus and, then, other types of plasma treatments are performed on the wafer by another substrate processing apparatus. The wafers are transferred lot by lot between the substrate processing apparatuses while being accommodated in a carrier.
Since the different substrate processing apparatuses perform different plasma treatments on the wafer, time required to perform predetermined plasma treatment on all the wafers of a single lot is different between the substrate processing apparatuses. Therefore, a substrate processing apparatus for performing second half steps of the semiconductor device manufacturing process may be in a standby state (idle state) until the completion of the plasma treatment of all the wafers of a single lot in a substrate processing apparatus for performing first half steps.
In the idle state, the processing module of the substrate processing apparatus does not perform plasma treatment. Therefore, the state in the processing chamber of the processing module is changed from the state most suitable for predetermined plasma treatment. If the idle state is excessively long, the state in the processing chamber may be changed to the state unsuitable for the predetermined plasma treatment. Therefore, before the predetermined plasma treatment is performed on each of wafers of a following lot in a carrier, dummy treatment similar to the predetermined plasma treatment is performed on a dummy wafer that has been loaded into the processing chamber. As a consequence, the state in the processing chamber is changed to the state suitable for the predetermined plasma treatment. Whether or not the dummy treatment is required is determined based on whether or not a period of time of the idle state is longer than a predetermined period of time (see, e.g., Japanese Patent Application Publication No. 2006-121030.)
Since, however, the dummy treatment is essentially unnecessary, even if it is performed only a few times, the throughput is decreased. Moreover, the cost is increased due to a dummy wafer required for the dummy treatment.